<meta charset="utf-8">
(#) Back button

!!! WARNING: Back button
   This is a warning.

Id
:   `BackButton`
Summary
:   Back button
Note
:   **This issue is disabled by default**; use `--enable BackButton`
Severity
:   Warning
Category
:   Usability
Platform
:   Android
Vendor
:   Android Open Source Project
Feedback
:   https://issuetracker.google.com/issues/new?component=192708
Since
:   Initial
Affects
:   Resource files
Editing
:   This check runs on the fly in the IDE editor
See
:   https://d.android.com/r/studio-ui/designer/material/design
Implementation
:   [Source Code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-checks/src/main/java/com/android/tools/lint/checks/ButtonDetector.java)
Tests
:   [Source Code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-tests/src/test/java/com/android/tools/lint/checks/ButtonDetectorTest.java)
Copyright Year
:   2012

According to the Android Design Guide,

"Other platforms use an explicit back button with label to allow the
user to navigate up the application's hierarchy. Instead, Android uses
the main action bar's app icon for hierarchical navigation and the
navigation bar's back button for temporal navigation."

This check is not very sophisticated (it just looks for buttons with the
label "Back"), so it is disabled by default to not trigger on common
scenarios like pairs of Back/Next buttons to paginate through screens.

(##) Example

Here is an example of lint warnings produced by this check:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~text
res/layout/buttonbar.xml:183:Warning: Back buttons are not standard on
Android; see design guide's navigation section [BackButton]
    &lt;Button
     ------
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Here are the relevant source files:

`res/layout/buttonbar.xml`:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~xml linenumbers
&lt;?xml version="1.0" encoding="utf-8"?&gt;
&lt;LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" &gt;

    &lt;!-- Hardcoded strings, wrong order --&gt;
    &lt;LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content" &gt;

        &lt;Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="OK" /&gt;

        &lt;Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Cancel" /&gt;
    &lt;/LinearLayout&gt;

    &lt;!-- Hardcoded strings, right order --&gt;
    &lt;LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content" &gt;

        &lt;Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Cancel" /&gt;

        &lt;Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="OK" /&gt;
    &lt;/LinearLayout&gt;

    &lt;!-- @android:string resources, wrong order --&gt;
    &lt;LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content" &gt;

        &lt;Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@android:string/ok" /&gt;

        &lt;Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@android:string/cancel" /&gt;
    &lt;/LinearLayout&gt;

    &lt;!-- @android:string resources, right order --&gt;
    &lt;LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content" &gt;

        &lt;Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@android:string/cancel" /&gt;

        &lt;Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@android:string/ok" /&gt;
    &lt;/LinearLayout&gt;

    &lt;!-- @string/ok/cancel resources, right order --&gt;
    &lt;LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content" &gt;

        &lt;Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/cancel" /&gt;

        &lt;Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/ok" /&gt;
    &lt;/LinearLayout&gt;

    &lt;!-- @string/ok/cancel resources, wrong order --&gt;
    &lt;LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content" &gt;

        &lt;Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/ok" /&gt;

        &lt;Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/cancel" /&gt;
    &lt;/LinearLayout&gt;

    &lt;!-- Random name resources, right order --&gt;
    &lt;LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content" &gt;

        &lt;Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/giveup" /&gt;

        &lt;Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/resume" /&gt;
    &lt;/LinearLayout&gt;

    &lt;!-- Random name resources, wrong order --&gt;
    &lt;LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content" &gt;

        &lt;Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/resume" /&gt;

        &lt;Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/giveup" /&gt;
    &lt;/LinearLayout&gt;

    &lt;!-- Random name resources with varying case, wrong order --&gt;
    &lt;LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content" &gt;

        &lt;Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/resume2" /&gt;

        &lt;Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/giveup2" /&gt;
    &lt;/LinearLayout&gt;

    &lt;!-- Resources with only one of OK and Cancel, wrong order --&gt;
    &lt;LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content" &gt;

        &lt;Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/ok" /&gt;

        &lt;Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/abort" /&gt;
    &lt;/LinearLayout&gt;

    &lt;!-- Resources with only one of OK and Cancel, wrong order --&gt;
    &lt;LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content" &gt;

        &lt;Button
            android:layout_width="wrap_content" android:background="?android:attr/selectableItemBackground"
            android:layout_height="wrap_content"
            android:text="@string/send" /&gt;

        &lt;Button
            android:layout_width="wrap_content" android:background="?android:attr/selectableItemBackground"
            android:layout_height="wrap_content"
            android:text="@string/cancel" /&gt;
    &lt;/LinearLayout&gt;

    &lt;Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/goback" /&gt;

&lt;/LinearLayout&gt;
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

`res/values/buttonbar-values.xml`:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~xml linenumbers
&lt;?xml version="1.0" encoding="utf-8"?&gt;
&lt;resources&gt;

    &lt;string name="button"&gt; Button &lt;/string&gt;
    &lt;string name="ok"&gt; OK &lt;/string&gt;
    &lt;string name="cancel"&gt; Cancel &lt;/string&gt;
    &lt;string name="resume"&gt; OK &lt;/string&gt;
    &lt;string name="giveup"&gt; Cancel &lt;/string&gt;
    &lt;string name="resume2"&gt; Ok &lt;/string&gt;
    &lt;string name="giveup2"&gt;"CANCEL"&lt;/string&gt;
    &lt;string name="send"&gt; Send &lt;/string&gt;
    &lt;string name="abort"&gt;Abort&lt;/string&gt;
    &lt;string name="goback"&gt;'Back'&lt;/string&gt;

&lt;/resources&gt;
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

You can also visit the
[source code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-tests/src/test/java/com/android/tools/lint/checks/ButtonDetectorTest.java)
for the unit tests for this check to see additional scenarios.

The above example was automatically extracted from the first unit test
found for this lint check, `ButtonDetector.testBack`.
To report a problem with this extracted sample, visit
https://issuetracker.google.com/issues/new?component=192708.

(##) Suppressing

You can suppress false positives using one of the following mechanisms:

* Adding the suppression attribute `tools:ignore="BackButton"` on the
  problematic XML element (or one of its enclosing elements). You may
  also need to add the following namespace declaration on the root
  element in the XML file if it's not already there:
  `xmlns:tools="http://schemas.android.com/tools"`.

  ```xml
  &lt;?xml version="1.0" encoding="UTF-8"?&gt;
  &lt;resources xmlns:tools="http://schemas.android.com/tools"&gt;
      ...
      &lt;Button tools:ignore="BackButton" .../&gt;
    ...
  &lt;/resources&gt;
  ```

* Using a special `lint.xml` file in the source tree which turns off
  the check in that folder and any sub folder. A simple file might look
  like this:
  ```xml
  &lt;?xml version="1.0" encoding="UTF-8"?&gt;
  &lt;lint&gt;
      &lt;issue id="BackButton" severity="ignore" /&gt;
  &lt;/lint&gt;
  ```
  Instead of `ignore` you can also change the severity here, for
  example from `error` to `warning`. You can find additional
  documentation on how to filter issues by path, regular expression and
  so on
  [here](https://googlesamples.github.io/android-custom-lint-rules/usage/lintxml.md.html).

* In Gradle projects, using the DSL syntax to configure lint. For
  example, you can use something like
  ```gradle
  lintOptions {
      disable 'BackButton'
  }
  ```
  In Android projects this should be nested inside an `android { }`
  block.

* For manual invocations of `lint`, using the `--ignore` flag:
  ```
  $ lint --ignore BackButton ...`
  ```

* Last, but not least, using baselines, as discussed
  [here](https://googlesamples.github.io/android-custom-lint-rules/usage/baselines.md.html).

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